A conventional speculum comprises a plurality of dilator members or arms which are spread by an actuator for enlarging a body cavity. There are commonly two types of actuators, the lever type and the cam or iris type. The lever type actuator typically comprises a pair of handles each having one dilator arm arranged in a manner so that when the handles are squeezed together the dilator arms spread apart. An inherent drawback with most lever type speculums is that the levers or handles are disposed in the line of sight of the body cavity therefore obscuring a view of the cavity under examination and/or interfering with the placement of medical instruments.
In the iris type speculums, the dilator arms are moved outwardly in a spiralling motion. As a result, the arms must slide against the tissue in the cavity being examined which may cause pinching of the tissue or discomfort to the patient. A further disadvantage with the known iris type speculums is their relatively complex construction and manufacture which increases costs to the extent that the speculums are in general, intended for multiple use. This therefore necessitates a strict hygiene and sterilisation program to ensure that there is no cross infection between patients. Accordingly, the use of iris type speculums is generally inconvenient to practitioners and increases the cost of service.
A further generation of speculums is known in which a rotating annular cam bears against the side of pivotal dilator arms causing the arms to pivot outwardly. An example of such a speculum is shown in Applicant's International application no. PCT/AU96/00125 (WO 96/28083). While this type of speculum has several advantages over the lever and iris type speculums described above, it is still relatively complex in manufacture requiring the production of numerous separate components which must then be assembled into the complete speculum.